This invention relates to a hematology control which is useful for clinical hematology procedures and, particularly, mean corpuscular volume (MCV) determinations.
Hematology control products are widely used as quality control materials to monitor determination of blood cell values in various established clinical hematology procedures. Specific blood cell measurements that are made by these procedures are white blood cell counts (WBC), red blood cell counts (RBC), hemoglobin content (Hgb), hematocrit (Hct) or packed cell volume, mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH) and mean corpuscular hemoglobin concentration (MCHC). The function of the hematology control product is to provide a means of ascertaining the accuracy and precision of these specific blood cell measurements in which the control is used in the same manner as the patient's specimen in the analysis procedure.
Hematology control products for the above clinical hematology procedures are well known. In these prior art products, human or animal cells having known values are often employed in aqueous suspension such as saline and buffered saline, or synthetic particles such as latex or other inert particles are used to simulate human blood cells, usually the white cells, in the suspension. Cells for these hematology control products also have been known to be stabilized such as by fixation with aldehydes or tannic acid. Thus, U.S. Pat. Nos. 3,574,137 and 3,640,896 disclose hematology controls comprising an aqueous suspension of fresh human red blood cells and tanned fowl red blood cells such as turkey or chicken cells. The fowl red blood cells are stringently fixed with tannic acid and glutaraldehyde and are used in the composition to simulate human white blood cells for white blood cell counting purposes. After fixation, the cells are suspended in Alsever's Solution. U.S. Pat. No. 3,558,522 describes a hematology control comprising washed red blood cells and small latex particles (to simulate white blood cells) in an aqueous suspension of albumin. Alsever's Solution is used for washing the red blood cell component of the hematology control.
None of the above prior art hematology control products are readily adaptable to provide varying levels of MCV such as would be desirable for control purposes in the assay of patient specimens having wide fluctuations in this parameter. Instead, it has been customary practice in the hematology field to pre-select cells of the desired size for incorporation in the hematology control products.
A close relationship exists in various of the aforesaid hematology measurements. Thus, the red blood cells (RBC) or erythrocytes contain hemoglobin (Hgb) which is the essential oxygen carrier of the blood. The hematocrit (Hct) test measures the relative volume of the cells and plasma in the blood. Normally, the Hgb level is about 15 gm/dl of blood, with women showing values slightly lower than men. The average normal value of packed red cells (Hct) is about 47% of the blood volume in men and about 42% in women. From the RBC, Hgb and Hct values, certain important morphological characteristics of the blood can be defined, namely:
Mean Corpuscular Volume (MCV), PA1 Mean Corpuscular Hemoglobin (MCH), PA1 Mean Corpuscular Hemoglobin Concentration (MCHC) and Color Index (C.I.). PA1 one mOsm/Kg=freezing point lowering of 1.858 millidegrees C. PA1 wherein mOsm=millosmol. PA1 2.05 g dextrose, PA1 0.8 g trisodium citrate (dihydrate), and PA1 0.42 g sodium chloride PA1 Glucose 2.05%, PA1 Sodium Citrate 0.80%, PA1 Sodium Chloride 0.42%, and PA1 Citric Acid 0.055%. PA1 2.05 g dextrose, PA1 0.05 g citric acid, PA1 0.8 g sodium citrate, and PA1 0.45 g sodium chloride
The Hct also can be derived mathematically from an averaged value for the MCV. Anemias with MCV&lt;80.mu..sup.3 are termed microcytic; with MCV&gt;94.mu..sup.3, macrocytic. Values of MCH, MCHC and C.I. of &lt;27 .mu..mu.gm, &lt;32 gm/dl and &lt;0.9, respectively, are indicative of Hgb deficiency, or hypochromia. Anemias with MCH and C.I. of &gt;32 .mu..mu.gm and &gt;1.1, respectively, are termed macrocytic; but because of the greater cell size, the MCHC remains normal. These various indicies aid in determining the nature of an anemia in a patient.
It is seen from the above that the preparation of a hematology control product with varying MCV levels to simulate normal as well as abnormally high or low would have significant use in the hematology field.
Accordingly, it is a primary object of the invention to provide a hematology control product and a method for its preparation in which the MCV can be readily adjusted to varying levels from abnormally low to abnormally high.